The use of endoscopes for diagnostic and therapeutic indications is rapidly expanding. To improve performance, endoscopes have been optimized to best accomplish their purpose. Therefore, there are upper endoscopes for examination of the esophagus, stomach and duodenum, colonoscopes for examining the colon, angioscopes for examining blood vessels, bronchoscopes for examining the bronchi, laparoscopes for examining the peritoneal cavity, and arthroscopes for examining joint spaces. The discussion which follows will apply to all of these types of endoscopes. Instruments to examine the rectum and sigmoid colon, know as flexible sigmoidoscopes, are good examples of the usefulness of this technology. These devices are expensive, used in a contaminated environment for a procedure which is brief (5-10 minutes) and where problems of cleaning time and contamination are important factors. There has been a large increase in the use of the "flexible sigmoidoscope" for use in screening symptomatic and asymptomatic patients for colon and rectal cancer. Ideally, flexible sigmoidoscopes must be used rapidly and inexpensively in order to maintain the cost of such screening at acceptable levels. Typically, a clinic would like to perform five to ten sigmoidoscope examinations each hour. One significant problem with making such examinations quick and inexpensive is the time necessary for adequately cleaning the device.
Although endoscopes can be cleaned in about two to four minutes, this relatively cursory cleaning may not be adequate for complete disinfection or sterilization. Even a more complete cleaning requiring on the order of eight to ten minutes may not allow adequate cleaning, particularly in view of the increasing problems with contagious viruses. Even with the use of chemicals such as gluteraldehyde, adequate cleanliness may not be possible.
While the external surfaces of endoscopes can often be adequately cleaned, endoscopes typically have air, water, biopsy and suction channels extending along their lengths which come into contact with body tissues or fluids. It is extremely difficult to adequately clean these channels even when skilled health practitioners spend a great deal of time on the cleaning procedure.
Even if endoscopes can be adequately cleaned in eight to ten minutes, the cleaning still prevents endoscopy examinations from being relatively inexpensive. While a physician may spend five to ten minutes performing the endoscopy, he or she will generally waste a great deal of time waiting for the endoscope to be cleaned before he or she can conduct another endoscopy. A partial solution to the "idle time" problem is to purchase multiple instruments so one can be used as the others are being cleaned. However, the expense of having duplicate endoscopes of each type makes this solution impractical especially for physicians' offices and smaller clinics.
Not only must the idle time of the physician be added to the cost of endoscopic examinations, but the time spent by a nurse or other hospital personnel in the cleaning as well as the cost of disinfecting chemicals must also be added to the cost of the examination. Although washing machines are available to clean endoscopes, these machines are expensive and not significantly faster than washing by hand. As a result, with conventional endoscopic procedures, both the physician and the relatively expensive endoscope have a downtime approaching fifty percent.
Another problem with cleaning endoscopes by hand or with a washing machine is that the chemicals used are toxic and potentially injurious to the staff who use them, and the environment into which they are discharged. To use some of these chemicals safely, such as gluteraldehyde, requires a dedicated ventilated hood, which uses up space and is expensive to install and operate. The chemicals are also potentially toxic to the patient in that if residue remains after cleaning and rinsing the instrument, the patient could have a reaction to the chemicals. A limitation to this approach is that some types of chemicals may damage the outer surfaces of endoscopes after a number of washings.
In short, conventional endoscope cleaning techniques greatly increase the cost of endoscopic procedures. Furthermore, while the risk of contamination using endoscopes is often far less than the risk of alternative procedures, such as surgery, there is nevertheless a risk that endoscopes are not adequately cleaned to prevent the risk of transmission of infectious diseases from one patient to the next.
In the health care field, the problems of contaminated instruments transmitting disease from one patient to the next have generally been solved by making such instruments disposable. However, this has not been thought possible in the field of endoscopy because endoscopes are very sophisticated, and hence, expensive instruments. Moreover, it has not been thought possible to isolate the endoscope from the patient or the external environment because the endoscope itself has channels inside it that are used as a conduit for body fluids and tissues, such as, for example, in taking biopsies. The only method currently available to actually sterilize an endoscope is to use gas sterilization with ethylene oxide gas. However, there are several significant disadvantages in using this procedure. The procedure is very slow; it takes 24 hours, during which the endoscope cannot be used. Also, the gas affects the the plastic of the endoscope and may limit the lifespan of the instrument. Finally, the gas is toxic, and, therefore, great care must be taken to ensure that no residue remains that might cause patient irritation during contact with the endoscope.
As a result of the above-described limitations in using and cleaning endoscopes by conventional techniques, there has not heretofore been an acceptable solution to the problem of making endoscopy procedures both inexpensive and entirely safe.